Air conditioning unit for vehicle

摘要

An air conditioning unit for cooling and dehumidifying a passenger room of a vehicle including a reciprocatory piston type refrigerant compressor having a refrigerant suction chamber, a compressed refrigerant discharge chamber, and an independent drive chamber for a drive mechanism to reciprocate compressor piston, a condenser, an expansion valve, an evaporator for thermal exchange, and an evaporating pressure control valve adjustably changing a fluid communication between the evaporator and the suction chamber of the compressor in response to a change is a cooling load. The air conditioning unit further includes a fluid bypass passageway providing a constant fluid communication between the evaporator and the drive chamber of the compressor regardless of the change in the cooling load so that a part of a lubricant containing refrigerant is always introduced into the drive chamber.